The present invention generally relates to mining machinery and more specifically to a mining machine adaptable to auger miners and constructed to retrieve unextracted coal or ore remaining from prior mining operations. The invention is also adapted to be used for original mining operations.
Coal is recognized as the most plentiful natural energy resource of general utility in many countries. However, coal has been a popular energy source for many decades and a great number of the richest coal fields have already been extensively mined. Coal is basically mined by two methods: surface mining and underground operations. The choice of method is dictated by many factors such as seam thickness, the depth and inclination of the seam, the location of the deposit, surface topography, economics and many other considerations. Surface mining is carried out by stripping away the strata overlying the coal seams and then removing the exposed coal. Over half the mining in the United States is accomplished in this manner. Thus, many surfaces have been strip mined leaving a large number of existing mined areas. Under certain conditions, a strip mining technique known as "auger mining" has been developed. The method comprises boring a series of parallel holes in coal seams which have been outcropped or have been exposed by removing overburden, leaving a highwall. The holes are cut by augers, large rotary drills ranging from two to five feet in diameter, which bore into the coal seam for some three hundred feet. The coal which is cut away by the auger is carried by the helical construction of the auger and is collected at the mouth of the hole. Augering machines are generally used where the thickness of the overburden is too great for removal but it can sometimes be used in an underground environment as well. Where auger mining can be used, it provides the most economical coal mining method.
As previously discussed, a typical conventional auger mining machine creates a bore of generally circular cross-section in a coal seam. Conventional auger miner devices are disclosed in U.S. Pat. Nos. 2,784,955; 3,105,677; 3,121,558; 3,190,698; 3,210,123; and 3,333,898, and a cutter head is discussed in U.S. Pat. No. 3,734,214. In auger mining, the auger is drilled into coal seams exposed by highwalls to remove the coal. The circular bores must be spaced far enough from each other to leave support pillars to prevent collapse of the seam. This spacing of circular holes typically leaves a significant amount of coal within the seam. In many mines, the circular bores are spaced much farther apart than is necessary to prevent collapse of the seam and the coal remaining in the seam is of high commercial value. In these mines, the maximum amount of coal is not recovered because of the shape of the bores and because the area or pillars in between the bores is wasted.
While the present application is directed toward the mining of coal, it will be appreciated that other ores or minerals which are found in seams or stratified deposits can also be mined. Consequently, the terms "ore", "minerals" or "materials" can be substituted for the term "coal", and use of the term "coal" should not limit the invention to this material, but should be considered to include all of the aforementioned materials.
A number of machines are known in the prior art for enlargement of circular bores or formation of rectangular bores. U.S. Pat. No. 4,082,362 discloses a mining machine with a circular boring head followed by two wing cutters, for horizontal enlargement of the initial circular bore. The cutters are driven in rotary fashion by cutting chains, which are in turn driven by a helical conveyor extending back to the mechanical power source. U.S. Pat. No. 1,880,091 discloses another mining machine with wing cutters, each cutter comprising a jaw with teeth on the periphery of the machine. The jaws are driven forward so that the teeth swing across the periphery of the bore and toward one another carrying with them coal scraped from the wall of the bore.
U.S. Pat. No. 1,978,366 discloses a dual chain-saw type mining machine. One chain-saw blade swings horizontally from a turret atop the machine and the other blade extends in front of the machine and is swung in a vertical plane.
Another type of mining machine comprises a rotary cutting drum extending forward from the machine. The drum is mounted on arms which transmit rotary power to the drum as well as lift the drum to cut coal above the height of the machine. The drums typically extend to the left and right of the width of the machine, so that a rectangular bore of substantial horizontal and vertical dimensions can be created by the cutting drum. Such machines are disclosed in U.S. Pat. Nos. 3,516,712 and 3,456,984.
A pertinent rotary cutting drum application is found in U.S. Pat. No. 3,712,679. This reference discloses a mining machine having a laterally extendable rotary mining head comprising a plurality of rotatable cutter support drums which are carried by a boom. The boom is pivoted on the housing and adapted to be moved by hydraulic cylinders. The cutting drums are powered by a pair of conventional rotary motors mounted on a catapillar vehicle. The coal cuttings are gathered by a gathering device comprising a gathering apron provided with gathering arms driven to direct material mined by the machine to a chain conveyor which carries the fragmented coal chips out to the entrance of the mine.
These prior art machines typically are constructed with a large number of moving parts which are subject to a high failure rate in a mining environment filled with dust. Machine failures in an underground environment are particularly difficult to rectify due to close quarters, lack of light, and lack of spare parts at hand. Further, such machines are typically quite expensive in single unit quantities. An article appearing on Page 7(d) of the Charleston Gazette, dated Friday, May 30, 1980, discusses a new thin seam coal mining machine which is reported in the article to sell for approximately two million dollars. A large portion of the cost of manufacturing such a machine lies in the provision of conveyor means and power supply which generally are already on hand at the normal mine site.